After egg-laying, we separated the resources and upon emergence of the F1 generation, we counted the distributions of the different morphs on each resource.
The deficit of heterozygotes in the early generations did not correspond to a lower viability of heterozygotes, as evident when comparing the number of adults that emerged of the different morphs (brown morph 548.0±45.1,; intermediate 512.0±28.0; black 459.3±4.09, mean ± SE number of adults, P = 0.67, Kruskal-Wallis test).
This observation does not contradict the male-biased expression, but further characterization of these genes would be interesting to gain a better understanding of their role in the growth of the different morphs.
The relationship between mating- and food preference was not immediately broken down as a result of gene flow between the different morphs, but instead lasted for a couple of generations.
These results suggest the pea aphid shows some lineage specialization in terms of energy costs, but a higher specialization in the production of the different morphs (e.g., winged parthenogenetic females).
Historically, some of the most important animals in studying colour polymorphism have been the land snails Cepaea nemoralis and the sister taxon, C. hortensis, because it is straightforward to collect them and record the frequencies of the different morphs in different locations and habitats (Cain and Sheppard 1950; Cain and Sheppard 1952; Cain and Sheppard 1954; Jones et al. 1977).
Anthers and stigmas of the different morphs were roughly at the same height.
The shell morphology of the different morphs from Meuse, Rhine, Rhône and Seine rivers was analysed.
In addition, the reproductive output of the different morphs may vary in the Gd Gm sexual system, which may be important to the stable maintenance of these morphs in the populations (Dufay et al. 2010).
Within-plant polymorphism for testa characters affecting germination is well known in the closely related C. album, where the ratio of the different morphs may be environmentally controlled (Harper, 1977).
